Note: Descriptions are shown in the official language in which they were submitted.
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ACID INHIBITOR COMPOSITIONS FOR METAL CLEANING AND/OR
PICKLING
FIELD OF THE INVENTION
[0001] This invention relates to acid inhibitor concentrates and solutions
prepared
therefrom which are useful for the acid pickling and/or cleaning of metal
surfaces.
BACKGROUND OF THE INVENTION
[0002] It is known to utilize certain compounds or mixtures of compounds in
acidic
solutions that are utilized for cleaning or pickling metal surfaces to remove
therefrom
unwanted oxides, scale and other undesirable corrosion products. Such
compounds reduce
the tendency of the acidic cleaning solution to corrode the metal surface
without
interfering with the cleaning operation performed by the solution. Compounds
that
function in this manner are generally referred to as "acid inhibitors". In the
absence of
acid inhibitors, an acidic metal cleaning or pickling solution can cause
significant base
metal loss and also damage to the metal surface as a result of excessive
hydrogen
exposure.
[0003] The corrosion of metal surfaces by acidic cleaning solutions is caused
by the acids
present in the solution. Acids generally used in such metal cleaning or
pickling solutions
are the so-called "non-oxidizing" acids. Included in this category are
inorganic (mineral)
acids such as hydrochloric acid, phosphoric acid, sulphamic acid, sulphonic
acid and
sulfuric acid and organic acids such as acetic acid, citric acid, formic acid,
glycolic acid
and oxalic acid.
[0004] The acid component of the cleaning solution is effective in removing
undesirable
deposits from metal surfaces, but unfortunately it also tends to attack and
corrode the base
metal. Such corrosion is obviously very undesirable. To counteract the
corrosive effects
of the acid, acid inhibitors are added to the cleaning solution.
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[0005] An effective inhibitor must disperse throughout the pickling solution
in low
concentrations, must suppress hydrogen evolution, and must not leave excessive
smut or
residual film on the surface of the metal. It must also maintain effectiveness
over a range
of acid and iron concentrations and temperatures, with such effectiveness
being long
lasting so that the metal pickling or cleaning solution need not be frequently
discarded or
replenished.
[0006] Many types of acid inhibitor compositions are known in the art, with
several being
available commercially. However, in many cases such formulations contain
undesirably
high concentrations of certain substances such as formaldehyde or acetylenic
alcohols
which are toxic and/or flammable and thus are subject to strict regulation due
to
environmental, health and safety concerns. Further, it is desirable for cost
and
convenience reasons to market such acid inhibitor compositions in the form of
concentrates that are diluted and combined with aqueous acid solutions to
prepare a metal
pickling or cleaning solution. Alternatively, such concentrates are used to
replenish
working metal pickling or cleaning solutions that have become depleted or that
no longer
have the desired degree of effectiveness with respect to acid inhibition. Acid
inhibitor
concentrates must remain stable over prolonged periods of time so that they
may be safely
stored until being combined with aqueous acid to form or replenish a metal
pickling or
cleaning solution. That is, the concentrate should remain a homogeneous
solution (e.g., no
phase separation or precipitation of solids) and should not deteriorate or
degrade in
effectiveness to a significant extent. Moreover, the solutions prepared from
such
concentrates must meet stringent customer requirements with respect to cost
and
perfoiniance (e.g., inhibition of metal etching), both immediately and over
time (e.g., as
iron levels in the solution increase upon continued use of the solution).
[0007] Further improvements in the art of acid inhibitor concentrates and
metal cleaning
and pickling solutions would therefore be desirable.
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BRIEF SUMMARY OF THE INVENTION
[0008] The present invention provides an acid inhibitor concentrate comprising
water, at least one
quaternized polyamino-aldehyde resin and at least one compound selected from
the group
consisting of acetylenic alcohols, ethoxylated fatty amines, ethoxylated fatty
amine salts and
aldehyde-releasing compounds. Such concentrates form useful metal cleaning and
pickling
solutions when combined with aqueous acid. These solutions, when contacted
with a metal surface
such as a steel, aluminum alloy, or zinc surface, are effective in removing
scale and other deposits
from the metal surface while exhibiting a reduced tendency for the aqueous
acid to attack or etch
the metal itself. The metal cleaning and pickling solutions of the present
invention, as compared to
solutions prepared using conventional types of acid inhibitors, exhibit
particularly good protection
against base metal etching when the solution contains high levels of iron and
is maintained at a
relatively high temperature over an extended period of time.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION
[0009] The acid inhibitor concentrates of the present invention may contain
one or more
polyamino-aldehyde resins. Such resins may be described as the reaction
products of polyamine
compounds and aldehydes and preferably are sufficiently water soluble at 25
degrees C so as to
permit their incorporation into the concentrates at levels of at least about 1
weight %, preferably at
least about 2 weight %, most preferably at least about 3 weight %. Although
acid inhibitor
concentrates based on non-modified polyamines (i.e., polyamines that have not
been reacted with
aldehyde) also exhibit some degree of acid etch inhibitory effects, modifying
the polyamine with
aldehyde has been found to provide significant enhancement in performance. The
enhancement is
particularly pronounced, for example, where an iron-containing substrate is
contacted with an HC1-
containing solution at elevated temperatures and/or in the presence of
dissolved iron and where an
aluminum-containing substrate is contacted with an HC1-containing solution at
elevated
temperatures. The polyamino-aldehyde resins may be in cationic, salt and/or
quaternized form so
as to increase their water solubility and/or effectiveness to the desired
extent. Water-miscible
organic solvents such as glycol ethers, glycols, ketones, alcohols, esters and
the like may
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also be used to solubilize the polyamino-aldehyde resin (and other organic
components) in
the concentrate, but preferred concentrates in accordance with the present
invention
contain no or essentially no (e.g., less than 1 weight %) volatile organic
solvents.
Preferably, the components of the acid inhibitor concentrate are selected such
that the
closed cup flash point of the concentrate is greater than 80 degrees C
(alternatively, greater
than 100 degrees C).
[0010] The polyamine compounds suitable as starting materials for the
polyamino-
aldehyde resin may be generally described as organic compounds containing two
or more
(e.g., three, four, five or six or more) nitrogen atoms per molecule and
preferably are water
soluble. For example, the polyamine compound may be prepared by polymerization
or
oligomerization of one or more nitrogen-containing monomers or by condensation
of two
or more nitrogen-containing substances. Such polymerization, oligomerization
or
condensation may involve other molecules in addition to the nitrogen-
containing
monomers or nitrogen-containing substances. For example, non-nitrogen
containing
compounds may be utilized as comonomers and/or as polymerization initiators.
[0011] Generally speaking, it is desirable for the polyamine compound to
contain a
plurality of nitrogen atoms (e.g., three or more or four or more or five or
more nitrogen
atoms) in the backbone of a polymeric chain containing covalently bonded
repeating units
or moieties. For example, the ratio of nitrogen atoms to carbon atoms
preferably may be
at least about 0.2, more preferably at least about 0.4. It will generally be
preferred for the
nitrogen atoms to be present in the form of amine groups, which may be
primary,
secondary, tertiary or quaternary in structure. The number average molecular
weight of
the polyamine is not believed to be particularly critical and may, for
example, be as low as
200, 400, 600, 800, 1000 or 2000 daltons and as high as 2,000,000, 1,000,000,
750,000,
500,000, 250,000 or 100,000 daltons.
[0012] Polyalkylenepolyamines (sometimes also referred to as
polyalkyleneimines or
polyalkylenimines) represent a particularly desirable type of polyamine
compound for use
in preparing the polyamino-aldehyde resin. Such materials are well-known in
the art and
are described, for example, in U.S. Pat. Nos. 2,182,306; 3,033,746; 2,208,095;
2,806,839;
2,553,696; and 3,251,778.
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The polyalkylenepolyamines which can be used as starting materials for the
polyamino-
aldehyde resins used in the acid inhibitor concentrates contemplated by the
present
invention include the oligomeric and polymeric materials that can be prepared
by reacting
ammonia or other nitrogen-containing compounds with alkylene dihalides (e.g.,
ethylene
dichloride) or by the ring-opening polymerization of substituted or
unsubstituted 1,2-
alkyleneimines (e.g., ethyleneimine). The polyalkylenepolyamine may be linear
or
branched in structure and may contain some crosslinking. The nitrogen atoms
present in
the polyalkylenepolyamine may be primary, secondary, tertiary, and/or
quaternary (i.e.,
ammonium). Polyethylenepolyamines may be obtained from commercial sources such
as
BASF, which sells certain polyethylenepolyamines under the trademarks
"Polymin" and
, "Lupasol". Suitable polyethylenepolyamines include oligomers and polymers
comprised
of repeating units having the structure (-Cli2CH2N1-1-), although other types
of repeating
units may also be present.
[0013] Suitable polyalkylenepolyamines also include copolyraers of different
imines as
well as copolymers of imines with non-imine monomers. The
polyalkylenepolyamine
may be modified or derivatized before being reacted with the aldehyde to torm
the
polyamino-aldehyde resin utilized as a component of the acid inhibitor
concentrates and
metal cleaning and pickling solutions of the present invention. As used
herein, the term
"polyalkylenepolyamine" includes all such modified or derivatized substances.
For
example, the polyalkylenepolyamine may be alkoxylated (e.g., ethoxylated,
propoxylated)
by reacting with an alkylene oxide such as ethylene oxide and/or propylene
oxide. The
polyalkylenepolyamine may also be acylated, alkylated, and/or olefinated. Such
derivatizations are described in more detail in U.S. Pat. Nos. 3,301,783 and
3,251,778.
[00141 Salts of the polyalkylenepolyamine or other polyamine may also be
utilized, with
such salts generally being formed by adding an acid to an aqueous solution of
the
polyamine compound.
[0015] Other suitable polyamine compounds may include, for example,
polyvinylamines,
polyallylamines, polyvinylguanidines, and the like.
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[0016] In one embodiment of the invention, the polyamine compound is
quaternized
(prior to reaction with aldehyde) in a known manner such as, for example, by
the reaction
thereof with one or more quatemizing agents.
[0017] Suitable quaternizing agents for reaction with the polyamine compound
include
the lower (CI-CIO) alkyl or alkenyl halides such as methyl chloride, methyl
bromide, or
methyl iodide; ethyl chloride, ethyl bromide, or ethyl iodide; or alpha
chloroglycerol;
dialkyl sulfates such as dimethyl sulfate, diethyl sulfate, dipropyl sulfates,
or dibutyl
sulfates; aralkyl halides such as benzyl chloride (an especially preferred
quaternizing
agent); lower alkyl esters of aryl sulfonates such as methyl toluene sulfonate
and methyl
benzene sulfonate; alkylhalo esters such as ethyl-chloroacetate; alkylene
halohydrins
such as ethylenechlorohydrin or alkylene oxides such as ethylene oxide or
propylene
oxide; alpha halo acetic acid derivatives, for example, alpha chloro ethyl
acetate, alpha
chloro acetamide, alpha chloro sodium acetate; haloketones such as
chloroacetone;
lactones, for example, propiolactone and sultones such as propane sultone. It
will be
appreciated by those skilled in the art that quatemization reactions do not
qasily go to
completion and usually a degree of substitution less than 100% (e.g., up to
40%, up to
60% or up to 80%) is achieved and can be quite effective for purposes of the
present
invention. Thus, it should be understood that it is possible that only a
fraction of the
nitrogen atoms in a quatemized polyamine compound may in fact be quatemized.
[0018] Particularly preferred polyamine compounds suitable for use in
preparing the
polyamino-aldehyde resins include those substances classified as CAS 68603-67-
8
("Amines, polyethylenepoly-, reaction products with benzyl chloride").
[0019] Quatemized polyamine compounds suitable for use in the present
invention are
also available from commercial sources, including, for example, CHEMQUAT SP-
1060
and CHEMQUAT SP-2060 (available from C&F Chemicals, Inc. of Exton,
Pennsylvania).
[0020] The aldehyde (aldehydes) which is (are) reacted with the polyamine
compound or
compounds to form the polyamino-aldehyde resin may be selected from the group
of
organic compounds containing one or more aldehyde (-CHO) functional groups (or
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equivalents or precursors thereof) per molecule. The aldehyde may be
aliphatic, aromatic
or araliphatic in character. Illustrative suitable aldehydes include
formaldehyde, C2-C6
aliphatic aldehydes (including dialdehydes), benzaldehyde, glutaraldeh.yde,
acetaldehyde,
paraformaldehyde, glyoxal, furfural, methylg,Iyoxal, malondialdehyde,
succindialdehyde,
and the like, with glyoxal being particularly preferred. The term "aldehyde"
as used
herein includes not only compounds containing one or more ¨CHO groups per
molecule,
but also equivalents and related derivatives, precursors or forms thereof
(including groups
capable of forming aldehyde groups in. situ). For example, in 40 % aqueous
solution,
glyoxal exists mainly in the form of a hydrated monomer, together with a
dioxolane dimer
and two bis(dioxolane) trimers. As will be explained later herein, aqueous
solutions of
glyoxal may conveniently be used in the preparation of the polyamino-aldehyde
resins
which can be a component of the acid inhibitor concentrates and metal cleaning
and
pickling solutions of the present invention.
100211 Reaction of the aldehyde(s) and polyamine compound(s) to obtain the
polyamino-
aldehyde resins utilized in the acid inhibitor concentrates of the present
invention may be
carried out under any suitable conditions known in the art for reacting such
types of
substances. However, it will generally be desirable to utilize conditions
effective to yield
resins having a relatively high degree of water solubility. That is, it is
preferred that the
resin produced be capable of being dissolved in water at 25 degrees C at
concentrations of
at least 5 weight %, alternatively at least 10 weight % or at least 20 weight
%. One
method of preparing the resins is to combine aqueous solutions of the
aldehyde(s) and
polyamine compound(s) in the desired ratio at ambient temperature. Exothermic
reaction
of these components will generally take place, with reaction generally being
substantially
complete within about 1 hour. If desired, catalysts and/or heating could be
utilized to
accelerate the rate of reaction.
[0022} In certain embodiments of the invention, the polyamine compound is not
reacted
with any other type of compound other than the aldehyde(s). For example, the
polyamine
compound is not reacted with a ketone or is not reacted with a fatty acid, but
with the
aldehyde(s) alone.
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[0023] Particularly preferred polyamine-aldehyde resins suitable for use in
the present
invention include those substances classified as CAS 78330-33-3 ("Amines,
polyethylenepoly-, benzyl chloride-quatemized, polymers with glyoxal"). Such
substances are also obtainable from commercial sources, such as the resin sold
under the
tradename "Chemquat JL-1060" by C&F Chemicals Inc., of Exton, Pennsylvania, as
well
as the resin sold under the tradename "Corrosion Inhibitor CBS -90" by
Consulting
Engineering Services, LLC, of Spartanburg, South Carolina.
[0024] Typically, acid inhibitor concentrates of the present invention contain
from about
0.5 to about 15 weight % (e.g., from about 1 to about 10 weight %) of
polyamino-
aldehyde resin. As those skilled in the art will appreciate, however, the
concentration of
resin may be varied as needed or desired depending, among other factors, the
extent to
which the concentrate will be diluted with aqueous acid to form a metal
cleaning or
pickling solution as well as the desired concentration of resin in the metal
cleaning or
pickling solution.
[0025] In addition to water and at least one polyamino-aldehyde resin, the
acid inhibitor
concentrates of the present invention may contain at least one aldehyde-
releasing
compound and/or at least one ethoxylated fatty amine and/or at least one
ethoxylated fatty
amine salt and/or at least one acetylenic alcohol. In one embodiment of the
invention,
however, the concentrate and the metal pickling and cleaning solution prepared
therefrom
are free of acetylenic alcohol.
[0026] The aldehyde-releasing compound is a compound which releases an
aldehyde
when foimulated into a metal pickling or cleaning solution containing aqueous
acid and
having a relatively low pH (e.g., less than about 4 or less than about 3) and
used to pickle
and/or clean metal surfaces having scale or other unwanted material deposited
thereon.
Preferably, the aldehyde which is so released or formed in situ is
formaldehyde. The
aldehyde-releasing compound preferably is water-soluble. Illustrative examples
of such
aldehyde-releasing compounds include, but are not limited to, Schiff bases,
formal,
acetaldehyde dialkyl acetals, trioxane, polyoxymethylenes, paraformaldehyde,
paraldehyde, condensation products of ammonia or primary amines with
aldehydes, and
the like. Preferably, the aldehyde-releasing compound has high water
solubility and low
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volatility. Compounds which are condensation products of ammonia or primary
amines
such as methyl amine with formaldehyde are preferred, condensation products of
ammonia
with formaldehyde are more preferred, and hexamethylenetetramine (also
sometimes
referred to as hexamine, methen.amine, urotropin, or urotropine) in particular
is most
preferred. Salts of such compounds may also be utilized.
[0027] Typically, acid inhibitor concentrates of the present invention may
contain from
about 1 to about 40 weight % (e.g., from about 5 to about 40 weight %) of
aldehyde-
releasing compound. As those skilled in the art will appreciate, however, the
concentration of aldehyde-releasing compound may be varied as needed or
desired
depending upon, among other factors, the extent to which the concentrate will
be diluted
with aqueous acid to faun a metal cleaning or pickling solution as well as the
desired
concentration of aldehyde-releasing compound in the metal cleaning or pickling
solution.
[0028] In certain desirable embodiments of the invention, the weight ratio of
aldehyde-
releasing compound to polyamino-aldehyde resin in the concentrate (and in
metal cleaning
and pickling solutions prepared from the concentrate) is within the range of
from about
0.5:1 to about 20:1 (e.g., about 1:1 to about 10:1).
10029] Suitable acetylenic alcohols for purposes of the present invention
include those
organic compounds containing both at least one ¨OH group and at least one
carbon-carbon
triple bond per molecule. Preferred acetylenic alcohols are water-soluble and
include C3-
C10 acetylenic alcohols such as, for example, 1-propyn-3-al, 1-butyn-3-ol, 1-
pentyn-3-01,
1-heptyn-3-ol, 1-octyn-3-ol, 1-nony1-3-01, 1-decyn-3-ol, 1-
ethynylcyclohexanol,
methylbutynol, 2-butyne-1,4-diol (a particularly preferred acetylenic
alcohol), 2-methy1-3-
butyn-2-ol, 2,5-dimethy1-3-hexyn-2,5-diol, benzyl butynol, alpha-ethynyl-
benzyl alcohol,
5-decyne-4,7-diol, 4-ethyl-1-octyn-3-ol, 2-propyn-l-ol (propargyl alcohol),
and the like
and mixtures thereof Alkoxylated derivatives of such acetylenic alcohols
(e.g., acetylenic
alcohols that have been reacted with 1 to 20 equivalents of one or more
epoxides such as
ethylene oxide and/or propylene oxide, such as ethoxylated propargyl alcohols)
may also
be used.
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[0030] Typically, acid inhibitor concentrates of the present invention may
contain from
about 0.5 to about 15 weight % (e.g., from about 1 to about 10 weight %) of
acetylenic
alcohol. As those skilled in the art will appreciate, however, the
concentration of
acetylenic alcohol may be varied as needed or desired depending, among other
factors, the
extent to which the concentrate will be diluted with aqueous acid to form a
metal cleaning
or pickling solution as well as the desired concentration of acetylenic
alcohol in the metal
cleaning or pickling solution. As mentioned previously, however, in certain
embodiments
of the invention the acid inhibitor concentrate and the solution prepared
therefrom do not
contain any acetylenic alcohol.
100311 To optimize the effectiveness and stability of the acid inhibitor
concentrates of the
present invention, it may be desirable to adjust the pH of the concentrate
solution by
adding effective amounts of acids or bases. For example, the concentrate may
be
formulated with one or more acids selected from the group consisting of
hydrochloric
acid, phosphoric acid, acetic acid, hydroxyacetic acid or other inorganic or
organic acids.
It will be understood by those skilled in the art that typically at least a
portion of the added
acid or base will combine with other substances used in the concentrate
formulation to
form salts, although some free acid or base may also be present in solution.
[0032] In one embodiment of the invention, the acid inhibitor concentrate
includes one or
more wetting agents, which generally help to improve the performance of the
cleaning and
pickling solutions prepared from the concentrate. Such wetting agents
typically are
surfactants, including in particular non-ionic and cationic surfactants. The
wetting agent
can, if desired, be selected so as to impart foaming properties to the metal
cleaning and
pickling solutions prepared from the acid inhibitor concentrates of the
present invention.
In one embodiment of the invention, however, one or more wetting agents are
selected
such that the resulting solution is essentially non-foaming (i.e., exhibits
substantially no
propensity to form foam when the solution is being used to treat metal
substrates).
Ethoxylated fatty amines and salts thereof represent a class of especially
preferred wetting
agents, as at least some members of this class appear to impart synergistic
performance
improvements to the acid inhibitor concentrates and acidic solutions prepared
therefrom.
In particular, it has been unexpectedly discovered that pickling or cleaning
solutions
containing at least certain ethoxylated fatty amines or salts thereof are
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effective in inhibiting base metal loss (i.e., lowering the etch rate) when
the solutions
contain relatively high concentrations of iron salts, especially when the
solution is being
utilized at a relatively high temperature. That is, the presence of such
ethoxylated fatty
amines or salts thereof tends to reduce the tendency of the pickling or
cleaning solution to
attack the base metal more aggressively as the solution is repeatedly used and
builds up
higher levels of iron salts. Illustrative ethoxylated fatty amines include
amines substituted
with one or more C6-C22 linear as well as branched aliphatic groups (including
alkyl
groups as well as alkylene groups containing one or more carbon-carbon double
bonds per
alkylene group) that have been reacted (ethoxylated) with from about 2 to
about 20 moles
of ethylene oxide per mole of amine as well as salts thereof (e.g.,
carboxylate salts such as
acetate salts). The ethoxylated fatty amine may be based on a diamine (e.g., a
compound
containing two nitrogen atoms per molecule, at least one of which is
substituted with one
or more C6-C22 saturated and/or unsaturated alkyl groups). Specific examples
of useful
ethoxylated fatty amines include ethoxylated coca amines, ethoxylated tallow
amines,
ethoxylated hydrogenated tallow amines, ethoxylated dodecyl amines,
ethoxylated
octadecylamines, ethoxylated soya amines, ethoxylated oleyl amines,
ethoxylated stearic
amines, ethoxylated N-tallow diamines, ethoxylated N-oleyl diamines, and salts
thereof
(for example, carboxylate salts such as acetate salts). Ethoxylated coca
amines containing
an average of from about 8 to about 16 (e.g., from about 10 to about 14) moles
of reacted
ethylene oxide per mole of coco amine, ethoxylated tallow amines containing an
average
of from about 6 to about 14 (e.g., from about 8 to about 12) moles of reacted
ethylene
oxide per mole of tallow amine as well as salts of such ethoxylated coca
amines or
ethoxylated tallow amines are particularly preferred. Such wetting agents are
readily
available as commercial products, including surfactants sold under the
tradename
"Cherneen" by Chemex, Inc., surfactants sold under the tradename "Varonic" by
the
Goldschmidt Chemical Corporation, as well as surfactants sold under the
tradenames
"Ethomeen" and "Ethod-uomeen" by Akzo Nobel. Other types of wetting agents
that can
be utilized include, for example, ethoxylated nonylphenols, ethoxylated
alcohols,
ethoxylated fatty acids, fluorosurfactants and the like. In one embodiment of
the
invention, however, the concentrate and the metal cleaning and pickling
solution are free
of fluorosurfactant.
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[0033] Suitable ethoxylated fatty amines can have the formula:
RN-(CH2CH20)n-H
(CH2CH20)1n-H
wherein R is a straight-chain or branched, saturated or unsaturated aliphatic
group having
from 6 to 22 carbon atoms, n and m are the same or different and each
preferably are at
least 1 and n + m is from 2 to 20. Mixtures of such compounds may also be
utilized.
[00341 Typically, acid inhibitor concentrates of the present invention contain
from about
0.1 to about 5 weight % (e.g., from about 0.5 to about 3 weight %) of wetting
agent (in
particular, ethoxylated fatty amine). As those skilled in the art will
appreciate, however,
the concentration of wetting agent may be varied as needed or desired
depending, among
other factors, the extent to which the concentrate will be diluted with
aqueous acid to form
a metal cleaning or pickling solution as well as the desired concentration of
wetting agent
in the metal cleaning or pickling solution.
[0035] In certain desirable embodiments of the invention, the weight ratio of
wetting
agent to polyamino-aldehyde resin in the concentrate (and in metal cleaning
and pickling
solutions prepared from the concentrate) is from about 0.05:1 to about 3:1
(e.g., about 0.1
to about 2:1). In other desirable embodiments of the invention, the weight
ratio of wetting
agent to aldehyde-releasing compound in the concentrate (and in metal cleaning
and
pickling solutions prepared from the concentrate) is from about 0.005:1 to
about 1:1 (e.g.,
about 0.02 to about 0.5:1).
[00361 To increase the water solubility of the polyamino-aldehyde resin in the
concentrate, it may be desirable to acidify the concentrate by adding an acid
such as
hydrochloric acid (at least a portion of the added acid may form salts with
the amine
groups of the polyarnino-aldehyde resin). However, a highly acidic solution
may tend to
accelerate the decomposition of the aldehyde-releasing compound to an
unacceptable
extent (thereby releasing aldehyde prematurely, that is, prior to the time the
concentrate is
used to make up a cleaning or pickling solution by combining with aqueous
acid). If the
aldehyde-releasing compound releases formaldehyde (a regulated substance), for
example,
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this may mean that the concentrate has to be specially handled to order to
avoid building
up unacceptably high concentrations of formaldehyde. For this reason, it may
be desirable
to package the concentrate as a two part system or kit, wherein one part
comprises an
aqueous solution of the aldehyde-releasing compound and, optionally, a wetting
agent
(such solution having a pH that is moderately alkaline, e.g., about 9 to about
10) and the
second part comprises an acidified aqueous solution comprising the polyamino-
aldehyde
resin (i.e., the aldehyde-releasing compound and the polyamino-aldehyde resin
are kept
separate until shortly before use, when the two parts of the concentrate are
combined and
diluted with aqueous acid to prepare the metal cleaning or pickling solution).
The second
part may optionally contain a wetting agent.
[00371 If maintaining the free formaldehyde level below 0.1 weight % in an
acid inhibitor
concentrate in accordance with the present invention is desired, it will
generally be
preferred to adjust the pH so that it is greater than about 7.
[00381 The acid inhibitor concentrates of the present invention will find use
in preparing
acid cleaning and pickling solutions that are effective in cleaning metal
surfaces of
unwanted metal oxide scale and other undesirable corrosion products. Examples
of such
cleaning solutions are those containing mineral and/or organic acids such as,
for example,
hydrochloric acid, phosphoric acid, hydrofluoric acid, sulphamic acid,
sulphonic acid,
sulphuric acid, acetic acid, citric acid, formic acid, glycolic acid, oxalic
acid and mixtures
thereof.
[0039] The concentration of acid in the metal cleaning or pickling solution
may be
adjusted as needed in order to achieve the desired level of cleaning activity.
For example,
where hydrochloric acid is utilized as the acid, typically the HC1 content of
the solution is
= maintained within the range of from about 1 to about 30 % (e.g., about 5
to about 20 %)
on a weight/volume basis. Typically, the acid(s) selected and the
concentration of such
acid(s) in the metal cleaning or pickling solution are effective to provide a
highly acidic
solution, e.g. a solution having a pH of less than about 3, less than about 2,
or less than
about 1.
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[0040] The acid inhibitor concentrates described herein can be utilized to
particularly
good advantage in applications involving strip line, continuous, and batch
hydrochloric
acid pickling of ferrous surfaces, that is, in applications wherein iron tends
to build up in
the cleaning solution. Various types of steel may be effectively cleaned of
scale and the
like by treatment with Ha-containing solutions prepared from the present acid
inhibitor
concentrates, for example. However, the acid inhibitor concentrates are also
useful in
other types of cleaning and pickling sOlutions, such as those, for example,
that are used to
clean aluminum or aluminum alloy surfaces or zinc or zinc alloy surfaces.
[0041] In general, the acid inhibitor concentrates of the present invention
are incorporated
into acidic cleaning solutions in any amount effective to reduce the tendency
of the acid to
attack and corrode without significantly interfering with the cleaning
operation performed
by the acid. The optimum amount of acid inhibitor concentrate to be combined
with an
aqueous acid solution will vary depending on a number of factors, including
the particular
active components present in the concentrate (e.g., the particular polyamino-
aldehyde
resin, the particular aldehyde-releasing compound, the particular wetting
agent, etc.), the
type and concentration of acid, the type of metal being treated, as well as
the treatment
conditions (e.g., contact time, temperature).
[0042] Typically, however, one part by volume of the acid inhibitor
concentrates of the
present invention is diluted with about 50 to about 50,000 parts by volume of
aqueous
acid. That is, the acid inhibitor concentrate typically is combined with an
aqueous acid
solution at a concentration of from about 0.001 to about 2 (e.g., about 0.005
to about 0.5)
% on a volume/volume basis. If the metal cleaning or pickling solution is to
be utilized at
a relatively high temperature, the amount of concentrate present in the
solution will
generally be higher than if the solution is to be contacted with metal
surfaces at relatively
low temperatures. The concentrate may first be combined with a relatively
concentrated
acid solution (e.g., 37% concentrated HC1) and the resulting mixture then
diluted with
water to yield the working solution that will be used to clean and/or pickle a
metal surface.
Such a mixture may also conveniently be used to replenish an existing solution
where the
acid concentration and/or the concentrations of acid inhibiting substances
have fallen
below the desired levels. Alternatively, the concentrate may be combined
directly with an
14
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aqueous solution having the acid concentration desired for purposes of the
cleaning and
pickling solution.
[0043] In certain embodiments, the metal cleaning or pickling solution may
contain
concentrations of components within the following ranges:
Polyamino-aldehyde resin 0.5-500 ppm (e.g., 1-200 ppm)
Aldehyde-releasing compound 0-1000 ppm (e.g., 5-500 ppm)
Wetting agent 0-200 ppm (e.g., 0.5-100 ppm)
Acetylenic alcohol 0-700 ppm (e.g., 5-300 ppm)
[0044] The above-stated concentration ranges are based on the amounts of the
individual
components as initially charged to the solution. Certain of the components, in
particular
the aldehyde-releasing compound, are believed to undergo chemical reaction or
=
transformation once the solution has been formed and/or once the solution is
placed into
use for cleaning and/or pickling metal surfaces. For example, without wishing
to be
bound by theory, it is believed that the aldehyde-releasing compound
decomposes to foim
aldehydes and other decomposition products after being combined with aqueous
acid to
form the metal pickling or cleaning solution, since such solutions are
typically highly
acidic and the aldehyde-releasing compound is known to be unstable at low pH
(e.g.,
where the pH is less than 3).
[0045] Generally speaking, cleaning and pickling solutions containing the acid
inhibitor
concentrates of the present invention can be utilized to treat any of a
variety of metals.
Examples of metal surfaces include both pure metals and alloys such as, for
example,
aluminum (including aluminum alloys), magnesium, zinc, titanium, iron, copper,
steel
= (including, for example, cold rolled steel, hot rolled steel, galvanized
steel, alloy steel,
carbon steel), bronze, stainless steel, brass and the like. For example, the
substrate to be
contacted with the solution may be comprised of at least 50 percent by weight
of
aluminum, zinc or iron. The substrate comprising the metal surface to be
treated in
accordance with the present invention can take any foim, including, for
example, wire,
wire mesh, sheets, strips, panels, shields, vehicle components, casings,
covers, furniture
components, aircraft components, appliance components, profiles, moldings,
pipes,
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frames, tool components, bolts, nuts, screws, springs or the like. The metal
substrate can
contain a single type of metal or different types of metal joined or fastened
together in
some manner. The substrate to be treated in accordance with the process of the
present
invention may contain metallic portions in combination with portions that are
non-
metallic, such as plastic, resin, glass or ceramic portions.
[00461 The metal cleaning or pickling solutions prepared from the acid
inhibitor
concentrates of the present invention exhibit good consistent inhibition of
metal etching
even when the solution is operated at relatively high temperatures over an
extended period
of time and/or contains a high iron loading level. For example, the solution
may be
maintained at temperatures of from ambient (i.e., about 20 degrees C) to about
100
degrees C. The metal surface with scale or other material deposited or adhered
thereon
which is to be cleaned and/or pickled is contacted with the solution for a
time and at a
temperature effective to remove the desired amount of scale or other material
from the
metal surface, leaving a cleaned and/or descaled and/or pickled surface with
reduced loss
(etching) of the metal itself as compared to contacting with the same type of
solution
which does not contain an acid inhibitor concentrate in accordance with the
present
invention. The solution may be brought into contact with the metal surface
using any
suitable or known method such as, for example, dipping (immersion), brushing,
spraying,
roll coating, wiping, and the like. Once the solution has been in contact with
the metal
surface for the desired period of time, the substrate having the metal surface
may be
removed from contact with the bulk of the solution (for example, by extracting
the
substrate from a tank or vat containing the solution). Residual solution
clinging to the
metal surface may be allowed to drain off the surface or removed by other
means such as
wiping. The metal surface may be rinsed with water or another solution to
remove any
remaining solution and/or to neutralize any residual acid and/or to prevent
"flash rusting"
of the freshly exposed metal surface. The metal pickling or cleaning solutions
of the
present invention are capable of producing easy to rinse metal surfaces
exhibiting the
"water sheeting" phenomena that clean, non-fouled, high energy metal surfaces
typically
exhibit. The "water sheeting" exhibited by rinsed metal surfaces processed in
accordance
with the present invention distinguishes the present invention from many acid
inhibitor
technologies known in the prior art, which tend to produce a very hydrophobic
"water
beading" surface (i.e., a metal surface on which water forms distinct separate
beads).
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"Water beading" on cleaned or pickled metal surfaces indicates that thin
organic films
have remained on the surface after the rinse step; such residual films may
adversely affect
and/or complicate further downstream processing of the metal-containing
article.
[0047] End uses of the compositions of the present invention include, but are
not limited
to, chemical and electrolytic pickling operations, acid dipping processes,
plant wash-out
procedures, cleaning of metal surfaces of industrial equipment (e.g., cleaning
industrial
boilers, heat exchangers and condensers), and oil well acidizing operations.
Examples
[00481 Example 1. To prepare a polyamino-aldehyde resin for use in foimulating
an acid
inhibitor concentrate in accordance with the present invention, 100 parts by
weight of an
aqueous solution of CHEMQUAT SP-1060 (a polyethylenepolyamine quaternized with
benzyl chloride; 60% solids) is combined with 30 parts by weight of a 40
weight %
aqueous solution of glyoxal. An exothermic reaction is observed, producing a
dark
colored solution exhibiting a strong absorption at 1640 cm-1 in the FTIR
spectrum.
[0049] Example 2. To prepare an acid inhibitor concentrate in accordance with
the
present invention, the following components are combined and mixed (preferably
in the
following order of addition) to yield a homogeneous solution:
Deionized water 65.05 wt. %
Hexarnethylenetetramine 16.0 wt. %
CHEMEEN C-1 2G ethoxylated coco amine 1.75 wt. %
Hydrochloric acid (20 degree baume) 9.75 wt. %
Acetic acid (56 %) 0.45 wt. %
Corrosion Inhibitor CES-901 7.0 wt. %
supplied by Consulting Engineering Services, LLC; reported to contain 59-61%
benzyl
chloride quatemized polyethylenepolyamine polymers with glyoxal (CAS 78330-33-
3),
less than 4% tetraethylenepentamine, less than 1% triethylenetetramine, and 39-
41% water
17
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[0050] To prepare metal cleaning or pickling solutions in accordance with the
present
reference, 1 part by volume of the above-described acid inhibitor concentrate
may, for
example, be combined with from 200 to 20,000 parts by volume of an aqueous
solution
containing 10 % weight/volume HC1. Other acids as well as other concentrations
of HCI
(e.g., about 0.5 to about 20 % weight/volume) may also be utilized.
[0051] The effectiveness of the pickling or cleaning solutions of the present
invention in
reducing the amount of base metal loss when the solutions are used to treat
metal surfaces
is demonstrated in the following examples.
Example 3
[0052] Solution A was prepared by combining 0.1710 g CHEMQUAT SP-1060
quaternized polyethylenepolyarnine with 2 L 10% weight/volume aqueous
hydrochloric
acid.
[0053] Solution B was prepared by combining 0.222 g of the polyamino-aldehyde
resin of
Example 1 with 2 L 10% weight/volume aqueous hydrochloric acid.
[0054] Solution C was prepared by first preparing a mixture of 130 parts by
weight of the
polyamino-aldehyde resin of Example 1 with 20 parts by weight of CHEMEEN C-12G
ethoxylated fatty amine and then combining 0.257 g of this mixture with 2 L
10%
weight/volume hydrochloric acid.
[0055] Cold rolled steel (1008 alloy) coupons measuring 0.032 x 2 x 4 inches
were wiped
with fresh isopropyl alcohol, dried, and weighed (to the nearest 0.1 mg). The
test panels
(2 per test) were suspended on plastic coated hooks through 'A" punched holes
and were
placed for 30 minutes in each of Solutions A, B and C, the solutions being
maintained at
180 degrees F, stirred with a magnetic stir bar (solution flow rate @ panels 3-
5
feet/second), and covered with water-cooled watch glasses. After the exposure,
the panels
were immediately rinsed in a fresh overflowing water bath, wetted with
isopropyl alcohol
and then fiinily wiped clean/dry with a fresh clean soft paper wiper before re-
weighing:
The test panels exhibited the following amount of base metal loss:
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Solution A: 0.5040 lb/ft2/hr
Solution B: 0.2935 lb/ft2/hr
Solution C: 0.2773 lb/112/hr
[0056] These results demonstrate that the reaction product of quaternized
polyethylenepolyamine and glyoxal (Solution B) was much more effective in
inhibiting
base metal loss than the unreacted quaternized polyethylenepolyamine (Solution
A) and
that the presence of an ethoxylated fatty amine (Solution C) also yields
additional
inhibition enhancement.
Example 4
[0057] Solutions A-1, B-1, and C-1 were prepared by adding 0.69 g
hexamethylenetetramine to each of Solutions A, B, and C, respectively, in
Example 3.
[0058] Following the same test protocol described above in Example 3, cold
rolled steel
coupons exposed to Solutions A-1, B-1, and C-1 exhibited the following amount
of base
metal loss:
Solution A-1: 0.1606 lb/ft2/hr
Solution B-1: 0.1220 lb/ft2/hr
Solution C-1: 0.0824 lb/ft2/hr
[0059] These results demonstrate that the presence of hexamethylenetetramine
further
enhances the effectiveness of the quatemized polyethylenepolyamine-glyoxal
resin in
= inhibiting base metal loss in a metal pickling or cleaning solution
containing non-
oxidizing acid (compare Solution B-1 with Solution B and Solution C-1 with
Solution C).
[0060] Solutions B-2 and C-2 were prepared by adding 0.24 g 1,4-butynediol to
each of
Solutions B-1 and C-1, respectively.
=
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[0061] Following the same test protocol described above, cold rolled steel
coupons
exposed to Solutions B-2 and C-2 exhibited the following amount of base metal
loss:
Solution B-2: 0.0710 lb/ft2/hr
Solution C-2: 0.0494 lb/ft2/hr
[0062] These examples demonstrate the benefits of including an acetylenic
alcohol in the
acid inhibitor compositions of the present invention.
Example 5
[0063] The effectiveness of the acid inhibitor concentrates of the present
invention in
inhibiting base metal loss during cleaning of an aluminum-containing substrate
is
demonstrated by the following examples. Two baths were prepared as follows:
Bath 1: 19.0 niL 37% HC1 diluted in 181 g deionized water.
Bath 2: 20 rnL of an inhibitor/acid mixture (the mixture being prepared from
13.4 g
deionized water, 72.6 rriL 37% HC1, and 0.475 g of an acid inhibitor
concentrate in
accordance with Example 2) diluted in 180 g deionized water.
[0064] Each bath was placed in a glass beaker at room temperature. Aluminum
panels
(3003 aluminum alloy; 2" x 4" x 0.025") were cleaned with SCOTCH-BRITE pads
and
water, then wiped with isopropanol, wiped dry and then weighed (to nearest
0.0001 g).
The panels were then placed in each of the beakers so that about two-thirds of
each panel
was immersed in the bath.
[0065] The panel immersed in Bath 1 exhibited significantly more gas evolution
than the
panel immersed in Bath 2. After 6 minutes of immersion, the weight of the
panel in Bath
I had decreased by 0.0066 g, while the weight of the panel in Bath 2 had
decreased by
0.0006 g (91% inhibition). Prior to weighing, the panels were rinsed and then
wiped with
isopropanol. After an additional 60 minutes of immersion, the weight loss of
the panel in
Bath 1 (which was cloudy and grey and had attained a temperature of 36 degrees
C due to
the exotherm created by dissolution of the metal) was 1.4436 g and the weight
loss of the
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panel in Bath 2 (which was clear and 67 degrees F in temperature) was 0.0137 g
(99.05%
inhibition). The panel that had been immersed in Bath 1 had a significant
amount of smut
on its surface, while the panel that had been immersed in Bath 2 had very
little smut on its
surface.
Example 6
[0066] To demonstrate the effectiveness of the inventive compositions in
inhibiting the
etching of a variety of aluminum alloy surfaces by hydrochloric acid, the
following test
solutions were prepared.
Control: 2.0 % (w/v) hydrochloric acid.
Invention: The acid inhibitor concentrate of Example 2 was diluted to 0.05%
(v/v) in 2.0
% (w/v) hydrochloric acid.
100671 Test panels of various aluminum alloys measuring 2" by 4" (two for each
test)
were cleaned using a SCOTCH-BRITE pad and water, then dried and weighed to 0.1
mg
accuracy. The panels were thereafter placed in 2 liters of the agitated test
solutions
(freshly prepared for each test and maintained at the temperatures shown in
Table 1) for
the times shown in Table I. The panels were then cleaned, dried and the metal
loss in
lbs/ft2/day calculated and compared to the control to determine the %
inhibition attained_
The results shown in Table 1 demonstrate that the bath in accordance with the
invention
generally exhibited a much higher degree of acid etch inhibition as compared
to the
control over a range of temperatures typically encountered during metal
cleaning
operations, no matter what type of aluminum alloy substrate was employed.
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Table 1.
Substrate % Inhibition, 38 C % Inhibition, 49 C % Inhibition, 60 C
1100 Al Alloy 82.0 72.3 43.9
2024 T3 Al Alloy 91.8 95.0 95.8
3003 Al Alloy 90.5 91.1 69.9
5052 Al Alloy 85.5 82.1 73.3
6061 Al Alloy 96.3 98.3 96.8
7075 T6 Al Alloy 81.0 57.8 63.6
Contact Time in 60/240 30/90 15/60
Minutes
(Control/Invention)
Example 7
[0068] To demonstrate the effectiveness of the inventive compositions in
inhibiting the
etching of pure zinc metal surfaces by phosphoric acid, the following test
solutions were
prepared.
Control: 5_0 (w/v) phosphoric acid.
Invention: The acid inhibitor concentrate of Example 2 was diluted to 0.05%
(v/v) in 5.0
% (w/v) phosphoric acid (1.06 g/2 L).
[0069] Test panels of pure zinc metal measuring 2" by 2" (two for each test)
were cleaned
using a SCOTCH-BRITE pad and water, then dried and weighed to 0.1 mg accuracy.
The
panels were subsequently suspended in 2 liters of the agitated test solutions
(freshly
prepared for each test) maintained at the temperatures shown in Table 2 for
the times also
shown in Table 2. The panels were then cleaned and dried and the average metal
loss in
lbs/ft2/day was calculated and compared to the control to determine the %
inhibition
attained. The results shown in Table 2 demonstrate that the bath in accordance
with the
invention exhibited an exceptionally high degree of acid etch inhibition as
compared to the
control.
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Table 2.
Test Solution % Inhibition, 38 C % Inhibition, 49 C % Inhibition, 60 C
Invention 95.6 95.1 91.9
Contact Time in 60/180 30/90 15/60
Minutes
(Control/Invention)
Example 8
[0070] This example illustrates the effectiveness of compositions in
accordance with the
present invention in inhibiting the acid etch of aluminum surfaces,
particularly when such
compositions contain both an aldehyde-releasing compound and an ethoxylated
fatty
amine.
[0071] The following baths were prepared:
Invention A ¨ 0.0742 g CES-90 (supplied by Consulting Engineering Services,
LLC;
reported to contain 59-61% benzyl chloride quaternized polyethylenepolyanaine
polymers
with glyoxal (CAS 78330-33-3), less than 4% tetraethylenepentarnine, less than
1%
triethylenetetramine, and 39-41% water) and 0.1696 g HMTA in 2 liters of 2.0 %
(w/v)
HC1.
Invention B ¨ 0.0186 g CHEMEEN C-12G ethoxylated coco amine was added to the
bath
of Invention A after such bath had been used (some acid consumed).
[0072] Two 2" x 4" panels of 3003 aluminum alloy (freshly cleaned using a
SCOTCH-
BRITE pad) were placed in each agitated bath, maintained at the temperature
indicated in
Table 3. After contact times identical to those listed in Table 1, the amount
of metal loss
was determined and the % inhibition calculated as compared to a control (2.0 %
w/v HO,
no inhibitor). The results obtained (Table 3) show that the use of a
quatemized
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polyethylenepolyamine that has been reacted with aldehyde (glyoxal) provides
effective
inhibition of acid etch, particularly at elevated temperatures and when used
in combination
with both HMTA and an ethoxylated fatty amine.
Table 3.
Temperature, Invention A, % Invention B, %
C Inhibition vs. Inhibition vs.
Control Control
38 89.3 92.3
49 87.6 90.6
60 63.0 79.9
24
